Deoxyadenosine Diphosphate as a Substrate and Inhibitor of Polynucleotide Phosphorylase of Micrococcus luteus: III. COPOLYMERIZATION OF ADENOSINE DIPHOSPHATE AND DEOXYADENOSINE DIPHOSPHATE

Abstract

Abstract Copolymers containing AMP and dAMP residues have been synthesized with polynucleotide phosphorylase from Micrococcus luteus. The rate of copolymerization depends upon the input ratio of ADP to dADP. It also depends, in a nonlinear way, upon enzyme concentration. Copolymerization proceeds most readily when Mn2+ replaces Mg2+ and preparation of polymers in Mn2+ therefore permits incorporation of a higher proportion of dAMP residues into copolymer. In the presence of either cation, the ratio of AMP to dAMP residues in copolymer is always higher than the ratio of ADP to dADP in the substrate mixture. The size of the copolymer poly (rAn,dAm) is quite large and identical to that of the homopolymer, polyA. Polymers synthesized in Mn2+ are more heterogenous in size than polymers synthesized in Mg2+. The Discussion includes a general discussion of the effect of Mn2+ on reactions catalyzed by M. luteus polynucleotide phosphorylase.